The present invention relates to an under-voltage tripping device with an early-operation auxiliary switch that is used as an external accessory for general-purpose, low-capacity circuit breaker, e.g. a molded case circuit breaker (auto-breaker) for controlling an electric motor.
The above molded case circuit breaker is provided with various optional accessories, including an under-voltage tripping device. The under-voltage tripping device is installed on a side of a breaker main body and linked with an internal mechanism of the main body so as to trip the breaker when the voltage at the main circuit decreases excessively during conduction.
Furthermore, an under-voltage tripping device with an early-operation auxiliary switch is known, in which an under-voltage tripping mechanism composed of an electromagnet and a tripping lever, and an early-operation auxiliary switch connected to a conductive circuit of the electromagnet and linked with a handle mechanism of the breaker, are combined and built into a single unit case, so that when the handle is operated to close a main circuit contact of the circuit breaker after the breaker has performed a tripping operation, the early-operation auxiliary switch can be turned on to reset the circuit breaker. This under-voltage tripping device with an early-operation auxiliary switch is used to simultaneously break the main circuit and a circuit for the under-voltage tripping device if the circuit breaker is applied to a circuit for emergency stop of loads on an electric motor or the like.
Before explaining the under-voltage tripping device with the early-operation auxiliary switch contact, a configuration of a circuit breaker, e.g. auto-breaker, is shown in FIGS. 6 and 7. In FIG. 6, reference number 1 denotes a circuit breaker, 1a is a case of the breaker main body, 2 is a current-interrupting section provided with a main circuit contact and an arc-extinguishing chamber, 3 is an opening-and-closing mechanism section for the main circuit contact, 4 is an over-current tripping device, and 5 is a rotary operation handle disposed on a cover top surface of the case 1a. The operation handle 5 constitutes a handle mechanism that connects a gear mechanism 6 linking the operation handle 5 with the contact opening-and-closing mechanism 3 to a reset cam for controlling a drive lever for the early-operation auxiliary switch of an under-voltage tripping device (accessory).
Opening and closing operations of the circuit breaker 1 are well known. When the operation handle 5 is rotated from the OFF position to the ON position, a toggle link mechanism 3a of the contact opening-and-closing mechanism section 3 operates via the gear mechanism 6 to close the main circuit contact of the current interrupting section 2 via an opening and closing spring 3b and an opening and closing lever 3c. Conversely, when the operation handle 5 is rotated from the ON position to the OFF position, the toggle link mechanism 3a and the opening and closing lever 3c operate in an opposite way to open the main circuit contact of the current interrupting section 2. Furthermore, when an over-current flows through the main circuit and causes the over-current tripping device 4 to release a latch mechanism 3d of the contact opening-and-closing mechanism section 3, the opening-and-closing mechanism section 3 opens the main circuit contact to interrupt the current. In this regard, the operation handle 5 follows this trip operation to stop at a TRIP position midway between the ON position and the OFF position, thereby indicating that the circuit breaker has performed a trip operation.
Furthermore, after the breaker has performed the trip operation, when it is tried to set the breaker after the main circuit has been restored to a normal condition, the operation handle 5 is returned from the TRIP position to the RESET position (same as the OFF position) in order to reset the latch mechanism 3d of the contact opening-and-closing mechanism 3. The operation handle 5 is then rotated to the ON position to close the main circuit contact in order to set the breaker.
Next, a basic structure and operation of the under-voltage tripping device with the early-operation auxiliary switch as an accessory, which is installed on a side of the main body of the circuit breaker for use, will be described with reference to FIGS. 8 and 9.
The under-voltage tripping device 10 is installed on a side of the case 1a of the circuit breaker 1 as an independent unit. A unit case 11 (the case 11 is made in a dimension so as to ensure that it does not protrude from the outward frame of the breaker main body) has external connection terminals (screw terminals) 12a to 12d arranged at the respective lateral ends thereof in different stages. The case contains the under-voltage tripping mechanism composed of a combination of an electromagnet 13 and a tripping lever 15 connected to the electromagnet, and an early-operation auxiliary switch 14 that opens and closes a conductive circuit for the electromagnet 13 in connection with the operation of a handle mechanism of the breaker main body. The external connection terminals 12a to 12d are arranged in different stages to facilitate a wiring operation required to install these terminals on a distribution board or a control board when connecting them to bus bars and branch bars of the main circuit laid in the board.
The tripping lever 15 has one end connected to an armature 13a of the electromagnet 13, and a drive pin 15a drawn out laterally from the upper end of the lever through the unit case 11 is linked with a tripping plate assembled on the contact opening-and-closing mechanism section 4 of the breaker main body. Reference number 15b denotes a return spring that forces the tripping lever 15 downward.
The early-operation auxiliary switch 14 is composed of two vertical sets of early-operation contacts, each of which include a pair of fixed contacts 14a and a bridge-shaped movable contact 14b bridging the fixed contacts 14a, and an oscillating contact holder 14c that supports the movable contacts 14b together with contact springs and journals the lower ends of the movable contacts. An operating lever 14d, which operates in connection with the contact holder 14c, is located at the upper end of the switch 14 and linked with a drive lever 16 integrated into a handle section of the breaker main body. Furthermore, the drive lever 16 is operated in connection with a reset cam 17 connected to the operation handle 5.
Furthermore, inside the case of the under-voltage tripping device 10, the above described external connection terminals 12a to 12d are wired as follows: the terminal 12a is connected to the terminal 12c through the upper early-operation contact of the early-operation auxiliary switch 14 and a coil of the electromagnet 13, and the terminal 12b is connected to the terminal 12d via the lower early-operation contact of the early-operation auxiliary switch 14. In operation, when the under-voltage tripping device is attached to the circuit breaker 1, the external connection terminals 12a and 12b are wired to the power supply side of the main circuit, while the other external connection terminals 12c and 12d are directly connected together, as shown in FIG. 10.
In the above configuration, when the operation handle 6 of the circuit breaker 1 is rotated to the ON position, the early-operation auxiliary switch 14 of the under-voltage tripping device 10 is turned on via the drive lever 16 to supply power from the main circuit to the electromagnet 13 of the tripping mechanism, thereby allowing electric conduction through the electromagnet 13. In this case, if voltage in the main circuit is normal, the attraction of the electromagnet 13 causes the tripping lever 15 to be pushed up against the spring force of the return spring 15b, and the drive pin 15a moves backward from the tripping plate of the opening-and-closing mechanism of the circuit breaker to maintain the main circuit contact in a set state. On the other hand, when the voltage in the main circuit decreases excessively, the spring force of the return spring 15b overcomes the attraction force of the electromagnet 13 to push the tripping lever 15 downward. Therefore, the tripping lever 15 pushes the tripping plate down to release the latch mechanism of the opening-and-closing mechanism. This causes the circuit breaker to perform the trip operation.
Furthermore, when the circuit breaker 1 is manually reset after a trip operation, the operation handle 5 is returned from the TRIP position to the OFF position and then rotated to the ON position. During this operation, the early-operation auxiliary switch 14 is turned on via the drive lever 16 operating in connection with the operation handle 5, thereby conducting electricity through the electromagnet 13. This conduction causes the armature 13a to attract the tripping lever 15 and pull it backward. Thus, the opening-and-closing mechanism section 3 of the circuit breaker is reset, and when the operation handle 5 is subsequently moved to the ON position, the main circuit contact of the current interrupting section 2 is closed.
The above-described under-voltage tripping device is connected to the main circuit of the circuit breaker 1 in order to apply the main circuit voltage to the electromagnet 13, as shown in FIG. 10. With this wiring method, if the main circuit voltage is high, the coil of the electromagnet 13 must conform to a high-voltage specification corresponding to the main circuit voltage. Therefore, to allow an under-voltage tripping device conforming to a standard specification to be applied to a high-voltage circuit breaker, a wiring method is required in which a transformer 18 is interposed between the early-operation auxiliary switch 14 and the electromagnet 13 so as to decrease the main circuit voltage, which is then applied to the electromagnet 13, as shown in FIG. 11.
When the wiring method shown in FIG. 11 is applied to the standard specification under-voltage tripping device 10 with the early-operation auxiliary switch described in FIGS. 8 and 9, wiring problems occur. That is, the under-voltage tripping device in FIGS. 8 and 9 comprises the four terminals 12a to 12d, each of which is connected to a corresponding end of the case 11 as external connection terminal, and the electromagnet 13 and early-operation auxiliary switch 14 are internally wired in series. Accordingly, the transformer 18 can not be externally connected unless it is modified.
In order to apply to the wiring method in FIG. 11, some products have an internal wiling configuration as described below. Namely, additional external connection terminals (screw terminals) 12e and 12f are installed in the case of the under-voltage tripping device 10 below the above-described external connection terminals 12a to 12d, and leads 13b, drawn out from the coil of the electromagnet 13 integrated into the case, are connected to the terminals 12e and 12f, as shown in FIG. 12. And, the early-operation auxiliary switch 14 is connected between the terminals 12a and 12c via a connection line 19, and a connection line 20 is used to connect the terminals 12b and 12d. 
With this configuration, the wiring method in FIG. 11 can be accommodated by externally connecting a primary coil of the transformer 18 (see FIG. 11) between the external connection terminals 12c and 12d, while connecting a secondary coil between the external connection terminals 12e and 12f. 
However, with the configuration in FIG. 12, the addition of the external connection terminals 12e and 12f increases the outside height H of the case 11 as compared to the standard under-voltage tripping device shown in FIG. 9. Thus, no problem occurs when the under-voltage tripping device is applied to a large circuit breaker, but in the case of a small circuit breaker, as its height is larger than the outside height of the circuit breaker, the under-voltage tripping device can not be installed in the breaker main body.
In other words, when a plurality of circuit breakers is installed on a distribution board or a control board, they are arranged and supported on support rails laid on the board, and their operation handles are made to protrude outward from a door of the board. This makes it nearly impossible to install tall under-voltage tripping devices in short circuit breakers.
The present invention has been made to resolve the above issues and to provide the under-voltage tripping device with the early-operation auxiliary switch that has the same size as existing standard under-voltage tripping devices and that also has an improved wiring structure in order to accommodate both wiring methods shown in FIGS. 10 and 11.
Further objects and advantages of the invention will be apparent from the following description of the invention.
According to the present invention, the above object can be achieved using the following aspects.
The first aspect of the invention provides an under-voltage tripping device with an early-operation auxiliary switch for a circuit breaker that is installed on a side of a breaker main body as an accessory to the circuit breaker. In the under-voltage tripping device, an electromagnetic under-voltage tripping mechanism and an early-operation auxiliary switch that opens and closes a conductive path for an electromagnet of the mechanism in connection with the operation of a handle mechanism of the circuit breaker are assembled in a single unit case comprising external connection terminals disposed at each of the opposite ends thereof. The single unit case is shaped to fit an outside frame of a breaker main body, and a wiring circuit for the electromagnet and a wiring circuit for the early-operation auxiliary switch are separated from each other in the unit case. The early-operation auxiliary switch is connected between the external connection terminals disposed at one end of the case and the external connection terminals disposed at the other end, and the electromagnet has leads drawn out directly from the case and connected to an external wiring.
In the second aspect of the invention, the unit case is shaped to fit the outside frame of the breaker main body, and the wiring circuit for the electromagnet and the wiring circuit for the early-operation auxiliary switch are separated from each other in the unit case. The early-operation auxiliary switch is connected between the external connection terminals disposed at one end of the case and the external connection terminals disposed at the other end, and the electromagnet has leads connected to the external wiring via a terminal block installed on one side of the unit case.
The above configuration uses the leads drawn out from the electromagnet coil contained in the case, or the terminal block disposed on the side of the case and connected to the leads. Accordingly, this configuration can be applied to the wiring method shown in FIG. 11 by connecting a transformer between the external connection terminals disposed at one end of the case and the external connection terminals disposed at the other end. Without any transformer, the leads from the electromagnet coil can be externally wired to the external connection terminals provided at the respective ends of the case.
Furthermore, the third aspect of the present invention provides another configuration wherein the under-voltage tripping device with the early-operation auxiliary switch is divided into two units. That is, the under-voltage tripping mechanism and early-operation auxiliary switch are separated and built into a unit case shaped to fit the outside frame of a breaker main body and comprising external connection terminals disposed at each of the opposite ends thereof. The two units are placed side by side and installed on a side of the breaker main body. In this installed state, the under-voltage tripping mechanism unit and early-operation auxiliary switch unit operate in connection with the breaker main body.